A disc brake system has excellent brake performance, so it is widely used in various vehicles. In general, the main structure of the disc brake system includes a disc and a caliper body disposed at the outer edge of the disc. The caliper body has an engaging trough corresponding to the disc and a pair of brake linings in the engaging trough. The brake linings are located at both sides of the disc, respectively. The caliper body has a plurality of piston chambers corresponding to the brake linings to accommodate pistons, respectively. The caliper body further has a passage in communication with the piston chambers. The passage is connected with the brake fluid tube of the vehicle. When the user pedals the brake pedal of the vehicle, the brake master cylinder of the vehicle feeds the brake fluid into the passage to push the piston, such that the brake linings are linked to clamp both sides of the disc so as to achieve the purpose of foot brake.
However, in addition to a foot brake function for driving, a vehicle also has a hand brake function for parking. For the caliper to have the hand brake function, the brake linings of the existing caliper are provided with a hook connected with a hand brake line of the vehicle. When the user pulls the hand brake lever, the brake linings are directly pulled by the hand brake line to clamp both sides of the disc so as to achieve the purpose of hand brake. With the development of science and technology, the current hand brake has been developed into an electric parking brake (EPB), so the aforesaid structure cannot be used directly. The foot brake and the hand brake of the aforementioned caliper use the same linings, which accelerates the wear of the brake linings. Besides, when the user releases the foot brake or the hand brake, the brake linings are unable to automatically leave both sides of the disc to cause noise and vibrations. Accordingly, the inventor of the present invention has devoted himself based on his many years of practical experiences to solve these problems.